>>Basically, in a Ufer ground system, you use either copper wires inside the
>>concrete tower base, or the rebar cage if you have one, as part of your
>>ground system. The tower is tied to the cage, and the cage is tied to a
>>soil ground radial/rod system.
>
>I always thought this was a big no no, because the rebar would then have a
>potential difference on it, and that would cause the water molecules to
>heat up during a lightning strike thereby causing the concrete to explode.
Polyphaser's book suggests you bond the rebar cage to a tower leg with 2/0
wire or strap and also bond the cage to the external ground field via
another 2/0 wire or strap.
I had two Polyphaser engineers assist me with designing my tower footing
and that is what they suggested.
My tower is surrounded on one side by a 180-degree ground field (to
disburse the surge energy away from the house). The ground field consists
of seven 50-foot radial grounds, spaced 30 degrees apart around the
180-degree arc.
The rebar cage is connected together by wire ties; no welding. The rebar
cage has eight 2/0 pigtails attached to it. Seven pigtails extend
horizontally below grade and connect to each ground radial. The eighth
pigtail extends vertically through the top of the footing and is bonded to
a tower leg. The J bolts are not bonded to the rebar.
73, Dick
--
Dick Flanagan W6OLD CFII Minden, Nevada (South of Reno)
--
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